The Pai River bridge is often cited as the most visible evidence of the presence of Japan's Army in Northern Thailand during WWII.
But the statement is incorrect. This website attempts to resolve that error, as well as other misconceptions about the period.

Lanna-ww2

Japan in Northwest Thailand during World War II

Lampang became the defense center for northwest Thailand probably because it had rail, road, and air transport facilities:

1. The Royal Thai Railway had connections south to Bangkok and its commercial port, Khlong Toei.

2. The Phahonyothin Road, the main north-south road in Thailand (now Route 1) provided a comparatively good land connection to Burma: north and then northwest to Kengtung, then westward to Meiktila and Mandalay on the Irrawady River, with rail, road, and air transport connections there.

The alternate choice would have been Chiang Mai, which was the northern railhead for the railroad and which had its own airfield, but lacked that critical existing quality road connection north into Burma. It was also rather more off-center geographically to the other military concentrations in northwest Thailand than was Lampang.

Imperial Japanese Army Air Force (IJAAF) units, early based at Lampang Airfield, flew support for Japan's successful 1942 invasion of Burma. Thereafter Lampang's importance declined as Japan's limited manufacturing base, confounded by Allied bombing, was unable to keep up with IJAAF losses and new aircraft were released direct to Japan's combat fronts in ever-decreasing numbers, and bypassing Lampang.

March 1940

Before the war, a US War Department report listed Lampang as a "military landing ground":[3]

When it was constructed has not been determined. It was located south of the City of Lampang at the same site as the current airport (with its runway marked in yellow below):[4]

An earlier runway's orientation was approximately perpendicular to the current runway and was referred to in Allied Intelligence reports as the "original" runway.[4a] The general location of that ENE-WSW runway can be ascertained from sketches in the various Allied intelligence reports which appear in the following chronological history. That orientation is evidenced on-the-ground today primarily by a building similarly aligned to one in a 1944 aerial photo from the Williams-Hunt Collection, plus scattered details barely visible in the latter.

1a.^ Lampang: the spelling of this transliteration is standard throughout all references found.

The name of the town has evolved over time from Lakhon (not to be confused with Lakon, aka Nakhon Sri Tammarat, south of the Isthmus of Kra), per Graham, WA, Siam: A Handbook of Practical, Commercial, and Political Information (London: Moring, 1913).

Further confusing is the name of the next major town to the northwest and connected by rail, Lamphun. To Western eyes and ears, the similarity of the two names, both starting with L, can be frustrating. In the case of Jack Newkirk, ace Flying Tiger pilot, it may have contributed to his early death: with orders to attack Lampang in late March 1942, he instead attacked Lamphun where he fatally crashed.

2.^ Lampang is located at the junction of major Thai Highways 1 and 11. Stationing needed.

The architectural style appears to be post-war. Curiously, different buildings appear at the same location with the same alignment with approximately the same exterior dimensions in a 1944 aerial photo of the airfield. The distinguishing difference appears mainly in the middle detail, between the two "sides":[4d]

Details common to both images are tagged. The purple line on the left traces current Thai Highway No 1037. The current runway center line is shown in dotted red (that it does not match perfectly between the two images may be due to distortions in the photo or perhaps the runway was later slightly realigned). The red‑circled buildings also appear similar in the two images.

The earlier runway is shown as a yellow center line. Its alignment parallels the building(s). It also parallels some obscure details on the left circled in blue. The yellow circled area denotes a long section of slightly different ground texture which is assumed to be a vestige of the old runway. A higher resolution image of the aerial photo markup may be downloaded here.

The heading of that earlier runway scales as 070°-250° (07-25). Such an orientation is unusual since runways are usually aligned to take advantage of prevailing winds in the region, which have been out of the north in recent history. In fact, those winds justify the approximate north-south orientation of the current runway. When the old runway was abandoned is unclear. While that earlier runway is referred to as the "original", the Lampang airstrip was once merely a large grassy area on which aircraft could land into whatever direction the wind was blowing.[4f]

1941

Lampang was not included in airmail routes in northwest Thailand in 1941:

That Lampang had not been included in the airmail system might have been the result of its proximity to the Chiang Mai railhead, 109 km northwest by rail.[5a] Chiang Mai was also nearer to the western border towns of Mae Hong Son and Mae Sariang, which were of particular concern to the Thai government because they were among the most remote areas of the country and comparatively lawless (even into the 1970s).[5b]

26-27 October 1941

Japanese aircraft, Ki-15s, were observed flying over the RAF airfield at Toungoo, Burma, at high altitude, obviously doing reconnaissance. Based in Hanoi, the flight path of the planes might have rendered them visible in various parts of Northern Thailand, including Lampang. Indeed, such aircraft might also have been observing various points throughout Thailand, including Lampang.[5c]

07 December 1941: A US Army Air Corps report, Airports in the Far East, probably conveniently redated to 07 December 1941, provided this information about the Lampang air facility:[6]

12 December 1941: Darrell Berrigan, an adventurous and prolific United Press reporter, fleeing north from Bangkok through Lampang and Mae Sai into British Burma, recorded on this date of having learned that the 'Lampang Airdrome' had just been occupied by IJA troops.[7]

Date uncertain, but about the same time, Christian missionaries from Chiang Mai, Nan, and Phrae traveled to Lampang from where they were bussed north to Mae Sai and crossed into Burma.[7҂]

22 December 1941: Local Chiang Mai photographer / historian Boonserm Satrabhaya recalled in his popular history of air activities around Chiang Mai:

When Field Marshal Phibun stationed army troops in the north at the beginning of the Great South East Asia War with Major General Jaroon Seri-reng-rit as northern commander-in-chief, the Royal Thai Air Force established a large air base at Lampang with Air Vice-Marshal Feun Ritakani as division commander coordinating with the army [which was also present].[7a]

• Williams-Hunt Aerial Photos Collection
• Original from the School of Oriental and African Studies (SOAS), University of London
• Digital Data from Center for Southeast Asia Studies (CSEAS), Kyoto University
• Digital Archive from Chulachomklao Royal Military Academy (CRMA), Thailand

6.^ US Army Air Corps, Airports in the Far East (Washington: Intelligence Division, Office of he Chief of the Air Corps, 07 Dec 1941), p 69 (USAF Archive microfilm roll A1285 p 0073). Significance of "(P9-18)" under column heading, Name, is not known.

6a.^ Difference with data in masthead reflects lesser accuracy available in 1941, plus use of the Indian-Thailand Datum (current datum is WGS84).

6b.^ These dimensions apparently refer to a period when air facilities were simply open ground allowing aircraft to take off and land in any direction. See Wikipedia's History of Aerodromes.

7.^ From the Sheboygan (Wis) Press, Thu 18 Dec 1941, p 12: "We left on the morning of Dec 11 [from Lampang]. The sealing of the frontier cut off escape for more than 60 Americans and 200 Britons left in Thailand. The next morning [12 Dec] Japanese troops were reported to have occupied the Lamping [sic] airdrome, blocking the northern route to Burma."

7҂.^ Kneedler, William Harding, MD, Refugeeing from Thailand in World War II, unpublished manuscript dated 1943 and located in Prince Royal's College Archives, Chiang Mai. See complete text on page 7: Refugeeing.

7a.^ Translation from บุญเสิม สาตราภัย
เชียงใหม่กับภัยทางอากาศ
(กรุงเทพฯ: วิญฌูชน, 2003)
Boonserm Satrabhaya
Chiang Mai and the Air War
(Bangkok: Winyuchon, 2003) [hereafter Boonserm], p 53 (translated by Wiyada Kantarod). Boonserm was concerned more in trying to encourage an interest by a Chiang Mai citizenry generally indifferent about local history than in getting every detail perfect.

Functions and aircraft ids are from Young, ibid, pp 184‑185 with "types" defined on pp 261-262.

Young records a far more complex process involving a comprehensive reorganization of the RTAF with reassignment of units to different commands and relocation of several commands to the far north of Thailand (pp 184-185). He also gives origins other than Ko Kha for the units:

22: Chantaburi
32: Isan
41: Lopburi

J-aircraft listings differ on two out of three units from the other sources. The units it lists were all originally located at Lopburi (per Young):

Thai military activities are presented in rather greater detail here because there are so few in-depth sources published in English.

8a.^ Dan Ford's Order of Battle 23 Dec 1941: 3rd Hikoshidan, 10th Hikodan. apparently quotes the 30 count from an order of battle dated 23 Dec 1941 presented in Japan's official military history, Senshi Sosho. However, on 04 Jan 1942, Ford records that the 77th sent out 31 Ki-27s to attack Rangoon. The 31 count, rather than the 30, is consistent with Ford's tally of losses between 23 - 27 Dec 1941: 1 loss on the 23rd and 4 on the 25th total 5. Subtracted from the original 36 leaves 31.

Richard Dunn in Double Lucky? (part 2) records "about 30 [IJAAF] operational fighters" in all of Thailand at first, all from the 77th Sentai.